Some commercial CAD software I use depends on many ksh (ksh93) scripts. In my test, those scripts work on mksh as well.

The original ksh93 has open-sourced in Oct 2017, and is being actively worked on (https://github.com/att/ast). However, they don't seem to have a release date in sight.
In this case, I think I will use mksh instead of ksh, at least for now.

@hashhsah it may be a bit obvious to state, but my method so far is to simply compile mksh and add it to the shell list.
Generating a eopkg build and posting it here can also be useful while it is not yet in the repo.

Anybody getting the tests to run properly in mksh using solbuild? Tests run perfect when building on my system, but as soon as I use solbuild, it complains about a missing tty (fd I think) and fails the check stage.